====== Rhythm perception ======

Humans (and some other animals*) have an innate sense of 'rhythm', i.e. the ability to detect and react with 'beats' in musical compositions.  Professional drummers and percussionists can 'beat time' with accuracies of just a few milliseconds per beat (ref. [[https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0026457|PLOS biology]] and [[https://link.springer.com/article/10.3758%2Fs13423-012-0371-2|Psychonomic Bulletin & Review volume 20, pp. 403–452]])

Non-musicians can also easily spot so-called 'swing' beats in music. Many jazz recordings use 'swing' as a means to introduce an attractive danceable 'groove' to the music (see 'Groove' section below)

In 'swing', one or two beats in each bar are deliberately delayed - but only by a few thousandths of a second. Nevertheless almost everyone can detect the difference between a 'swing' beat and a 'straight' beat. There is quite a body of research on how 'swing' is accomplished (example [[https://online.ucpress.edu/mp/article-abstract/19/3/333/61900/Swing-Ratios-and-Ensemble-Timing-in-Jazz|ref.]] ) but no agreed explanation as to how people can so easily detect it.

Implications are that the brain has an internal 'clock' (running at accuracies down to milliseconds) against which a performer can reference his/her motor outputs.

There are two main theories of how this might be happening. One is that the beats can be judged and reacted-to in an 'absolute' way (with reference to the mental clock) - the other is that the beats are judged 'relatively' to the previous beats (involving a 'memory' of the timings).

Experiments and observations of brain-damaged patients have located (at least some of) the brain areas where the 'clock' appears to be located.

>There is reasonable consensus that the cerebellum is involved in absolute timing mechanisms, and basal ganglia-thalamo-cortical circuits are involved in relative timing mechanisms.\\ \\ Source : [[https://link.springer.com/chapter/10.1007/978-1-4939-1782-2_17|Neural Mechanisms of Rhythm Perception: Present Findings and Future Directions ]]

But the underlying biological mechanisms which might be able to regulate a 'clock' at such accuracies are completely unknown.

There is also no explanation from an evolutionary standpoint as to why this highly accurate timing system might have evolved.

Longer periods (minutes, hours, days, weeks etc etc) of humans' time perception, which is also unexplained (and which may or may not be related to the beat perception clock) can be found here : [[content:psychology:general:time_awareness|Time Awareness]]

==== 'Groove' fMRI studies ====

The //[[https://ins-amu.fr/about|Institut de Neurosciences des Systèmes]]// (INS)  - a multidisciplinary research institute at Inserm and Aix-Marseille University, France, has published details of its 2023 fMRI work examining possible reasons why people relate strongly to so-called 'groove' beats in music. Particularly with regard to the urge to dance.

>[...] during auditory perception, the motor system encodes temporal predictions information and can optimize auditory processing. Recently, a Bayesian model of groove has been proposed, in which the experience of groove is related to predictive timing and more precisely correlates with the precision-weighted temporal prediction error computation during the processing of musical rhythms .\\ __However, the neurophysiology of groove is still unclear."__\\ \\ Source : [[https://www.science.org/doi/10.1126/sciadv.adi2525|Neural dynamics of predictive timing and motor engagement in music listening]]{{:oa_padlock_grn.png?16}}//ScienceAdvances,// Vol. 10, No. 10

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*Note : Several other animal species apparently respond to musical rhythms. A 2022 study found that rats appear to prefer musical beats at around 120 to 140 bpm (beats per minute). See : [[https://www.science.org/doi/10.1126/sciadv.abo7019|Science Advances]], Vol. 8, No. 45

A 2023 study, published in //Proceedings of the Royal Society B, //found that pairs of Gibbons often synchronise their 'songs' with each other - which implies they have a strong sense of musical rhythm. [[https://royalsocietypublishing.org/doi/10.1098/rspb.2022.2244|source]]

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Also see [[content:psychology:general:musical_appreciation|Musical Appreciation]] , [[content:life_sciences:human_body:core_clock|Core Clock]] and [[content:psychology:general:musical_pitch]]

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